In one aspect, this invention is related to means and method for facilitating management, storage and retrieval of programs on a cassette of magnetic tape. In another aspect, this invention is related to maintaining current information about a tape in a magnetic tape cassette and more particularly to maintaining current information about such a tape using a magnetic tape reader/recorder, and magnetic tape cassettes therefor.
Two general methods for long term mass storage of data are known; random access and sequential access. The random access method uses long playing (LP) record players, compact disc (CD) drives and video disc drives for consumer use, and hard disc drives, floppy disc drives and optical disc drives for use with computers. In all, information is accessed at random by moving a playing head directly over the desired playing area of the stored media.
a. Problems with Serial Storage Devices
In the sequential method, stored information can only be accessed sequentially. The sequential method uses audio tape drives, video tape drives and digital audio tape drives for general consumer use and digital tape drives and tape backup cassette drives for use with computers and analog tape drives for instrumentation purposes. All of these devices use magnetic tape as the stored media. The big advantage of tape drives is low cost compared with random access devices. The disadvantages and problems of using magnetic tape are three-fold.
i. To go to a particular location on tape, the tape must be either advanced or rewound in a serial or sequential manner. Unless forward or reverse operations can be performed at very high speed, this can be a time consuming process.
ii. The exact contents and location of records on the tape are not known. Random access devices can record (usually at the outermost tracks) an index of the content at the beginning of the disc and anytime the index information needs to be accessed, the read or write head simply skips over to read the index. For magnetic tape, even if the index is recorded in a reserved area at the beginning of the tape, as is presently done in some video tape or computer tape backup systems, its usefulness is limited, due to the time required to rewind the tape all the way to the beginning, assuming the tape is not at the beginning when the need arises to search for the index. owners of large numbers of tapes desire to place titles on the tapes to enable rapid identification of the program thereon. Usually titling is done by hand writing a title on a label on the tape or its box. However, the tape can become separated from the box, or the label may fall off. Some tape owners repeatedly record over the same tape and prefer not to use permanent labels. Computer tapes may contain hundreds of records or files and handwriting or updating the index onto the box is not practical.
iii. The absolute current location of the tape is not known. Most tape drives have tape counters which only indicate relative location. For example, if a tape cassette is played and then removed from a tape drive without rewinding, the next time the cassette is inserted and played by a tape drive, the absolute location of the tape in the cassette will no longer be known. Attempts have been made to overcome this problem by writing absolute address marks onto the tape. For example, some recent video tapes use the VHS Address Search System (VASS) whereby absolute address marks are written at 1 minute intervals onto the control track of a VHS tape. In computer backup of hard discs by tape, the streaming mode is usually used where a constant stream of data blocks (usually 512 bytes) are written onto the tape, each block being usually preceded by one or two address bytes. Thus, absolute addressing is available but not yet universally used on tape.
Knowing the absolute address is important. For example, assume that there are 5 programs (or records) on a tape and each of their starting addresses is known and a user desires to go to the starting location of program 4. Without knowing the absolute address of where the tape is currently positioned, the user or the drive has no way of knowing whether to rewind or fast forward the tape to reach the desired record.
In order for tape drives to compete against random access devices it is important that these three problems be either overcome or ameliorated.
b. Providing Program Titles
Placing a descriptive title on the tape presents another problem. Video titling is usually known and recorded on a leader portion of the tape. Ordinarily, the title is computer-generated and recorded in a sequence of regular video frames, rather than on the control track. If multiple copies of the tape are made, the quality of the title drops off drastically. Also, the title cannot be conveniently edited without re-recording the sequence of frames. Prior art systems for applying such titles are either expensive or cumbersome. Professional video titling systems include the well-known Chyron system and many others. Typically these systems include a complete computer, a complex, high-resolution character generator, a special effects generator for making shadows, italics and other effects, and a video interface to generate a video signal. Such systems are too expensive and complicated for the home video market.
Some videocassette recorders (VCRs) and camcorders are equipped with simple character generators for displaying simple block letters and numbers, either superimposed over a recorded video signal or recorded and mixed with the picture signal. A typical camcorder application is adding characters representing the recording date and time to a video signal as it is being recorded, thereby adding a xe2x80x9cdate stamp.xe2x80x9d In VCRs, the character generator can be used to show programming information such as channel, date, and time on screen as the VCR is being programmed to record programs at a future date. However, currently there is no simple way to use the VCR character generator as a titling device.
In xe2x80x9cRecommended Practice For Line 21 Data Services, Part Seven, Extended Data Service Packetsxe2x80x9d, Draft EIA-608, Oct. 12, 1992, there is suggestion of using VBI line 21, field 2 to send information such as program title and type along with the broadcast program. Yet, the possible use of such information for facilitating operation of a videocassette recorder, such as providing a title for a recorded program, is never suggested.
c. Title Editing
Another problem with prior art titling systems is data input and editing. With Chyron systems, a full-size typewriter-style keyboard is used which is inappropriate for home use and slow for poor typists. Editing of a title is impractical with most home-generated titles, because the title is recorded as a video image on the tape. Thus, the prior art fails to provide a convenient means for generating, storing, and editing video titles for use with sequentially-stored magnetic tape. Users of home video equipment would likewise appreciate a system using internal character-generator hardware and VCR remote controls, thereby precluding the need for complex or expensive hardware to generate titles.
It is an object of the invention that the addressing system provide a fast and accurate way of searching for the starting points of the programs. It is a further object that the addressing system determine the current position on the tape and provide a means of homing in to the destination address, during a search. It is yet another object of the address system to provide a means for accounting for the lengths of programs as they are recorded or modified.
It is an object of the invention to have a memory that is randomly accessible for storing the directory. It is another object of the invention that the directory be changeable without degrading the quality of the recorded information on the tape.
It is an object of the invention to provide a program guide that is broadcasted to the user and which provides current scheduling and descriptive information that includes special events which are scheduled on short notice. It is a further object that the program guide be usable for timer programming an Indexing VCR with minimal interaction by the user so that the user finds time shifting for viewing programs easier. It is yet another object that the broadcaster can provide increase the viewing of programs broadcasted during traditional off-hours.
It is an object of the invention to have an indexing VCR with greater reliability and utility and at a lower cost than the Moving Head System.
The invention provides, in a magnetic tape cassette reader/recorder, a method and apparatus for maintaining current information, such as a directory of recorded programs, about a tape in a magnetic tape cassette. The availability of the program directory can greatly facilitate operation of the tape cassette reader/recorder. For example, with a program directory, a user can perform an erase operation of a taped program by simply indicating on the directory that the program can be over-written and/or no longer accessible; or a recording operation by selecting from the directory a proper tape segment to perform the record operation without having to go through the tape to find the right spot. In brief, the availability of a program directory will eliminate much of the frustration that has been felt for so long by so many users of tape devices such as VCRs.
Different embodiments of the present invention are disclosed in the specification for storing current information about a tape. For example, in one embodiment, the information is kept in a secondary memory carried on the exterior of a tape cassette.
According to one implementation of the above embodiment, the secondary memory is a storage medium carried on the cassette. The storage medium preferably comprises a magnetic layer and an adhesive layer for affixation of the storage medium to the housing of the cassette. A stationary magnetic head/sensor is provided on the VCR to access the current information stored on the magnetic layer. The method of accessing the current information comprises the steps of reading the content on the magnetic layer after commencement of the insertion of such cassette in the reader/recorder, and causing the magnetic layer to be updated with current information about the tape therein whenever such cassette is ejected from the reader/recorder.
According to another implementation of the above embodiment, the secondary memory is also a magnetic layer carried on the cassette and preferably a magnetic layer affixed to the housing of the cassette. However, the magnetic head/sensor for reading/writing data on the magnetic layer is movable over the magnetic layer. Under such implementation, information about the tape can be read and written with more freedom than the above implementation which uses a stationary head.
According to another implementation of the above embodiment, the secondary memory for storing information of the tape is a semiconductor memory carried on the cassette. Preferably, the semiconductor memory has serial input/output so that the number of contact points for communicating addresses and data between the cassette and a VCR is minimized. Advantageously, storage of information into the semiconductor memory can occur at any preferred time between the update and ejection of the tape.
According to another embodiment of the present invention, directory information of a tape is recorded on the tape itself. The advantage of the embodiment is that the invention can be practiced without modification to the tape or its housing.
In one implementation of this embodiment, directory information is written on the video track of the tape in the vertical blanking intervals (VBI) of recorded video signals.
In another implementation, directory information is written on the control track of the tape. Preferably, a marker is formed on the tape to uniquely identify the position of a current directory. Also preferably, a first marker is recorded on tape in close proximity to a current directory when the directory is recorded on the tape. The tape is searched for a directory with the first marker. A second marker is recorded on the tape in close proximity to the first marker when the current directory is read. Alternatively, a marker may be recorded on the tape in close proximity to a current directory when the directory is recorded on the tape. The tape is searched for a current directory with the marker in close proximity thereto. The marker is erased when the directory is read. Also, the current tape position may be read from the housing of the cassette during insertion of the cassette into the reader/recorder. A current position of the tape may be written on the housing of the cassette during removal of the cassette from the reader/recorder.
In one embodiment, the directory is erased from the tape immediately after the step of reading the directory. In another embodiment, the reader/recorder re-positions the tape in the cassette, after reading the directory and prior to removal of the cassette, to a position such that the directory will be read out by the reader/recorder upon reinsertion of the cassette in the reader/recorder and prior to reading by the reader/recorder of one of the records from the tape. In still another embodiment, the tape is not rewound after the directory is read and prior to removal of the cassette; however, the tape is read for the directory in a reverse direction when it is reloaded.
Preferably there is recorded on the tape in association with the directory, a current position of the tape at which the reader/recorder will commence reading the tape upon reinsertion of the cassette in the reader/recorder. Also preferably, when reading the directory from the tape, the current position is also read from the tape and a representation of the current position is stored in the memory. Preferably, the current position in the memory is updated as the tape is being moved for reading or writing and the updated position may be recorded on the tape.
In still another embodiment of the present invention, directory information of a tape is stored in a random access memory located in the VCR. An identification (e.g. a volume label) is written on the tape whereby the corresponding directory information can be retrieved from the random access memory when the tape is loaded into the VCR.
Index information are provided on the tape to facilitate searching of programs recorded thereon and positioning the tape to selected programs.
According to one implementation, the index information is written at predetermined space intervals on the tape. The index information is represented by the value of the tape reel counter at the time the information is written. In one specific implementation, the index information is written onto the control track. In another specific implementation, the index information is written onto the VBI portions of the video track.
In another implementation, a cue signal is written at the beginning of each program. The address of a program is represented by its sequential position relative to other programs on the tape. A program under this implementation is located by counting the cue signals encountered during either a fast forward or a rewind operation, until the appropriate number of cue signals are encountered.
Different implementations are provided to further enhance the creation, maintenance and usefulness of the program directory. For example, in one embodiment, a program title, forming one part of the directory, is entered using controls on a jog shuttle remote control of the recorder/reader as an input device. A representation of an alphanumeric keyboard is displayed on a monitor screen by a character generator in the recorder/reader under control of the controller. Arrow buttons or a jog shuttle knob on the remote control can be used to select individual characters forming words in the program title. After the complete title is composed by a user it is saved in the directory. In another embodiment, a scrollable character is displayed instead of a keyboard representation. The arrow buttons or jog shuttle knob cause the character to change by stepping sequentially through the alphabets/numerals until a desired character is located.
In another embodiment, the controller is coupled to a decoder for decoding data (e.g. a program title) communicated in the VBI portions of a broadcast television signal. The decoded data is fed to the directory in the memory and also is displayed on a monitor screen. The displayed data can then be edited using controls on a jog shuttle knob of a VCR remote control. In one specifically contemplated embodiment, the decoder decodes data from line 21, field 2 of the VBI.
In another embodiment, the data communicated in the VBIs include data, such as a program title, which can be used to detect extension of a program beyond its scheduled time, thereby causing the VCR to continue recording the program.
In yet another embodiment, auxiliary information of a first program, such as the channel-date-time-length of a related second program is broadcasted in the VBI of the first program. In response to a user input, the auxiliary information is retrieved from the VBI and used for automatically setting the VCR to record the related second program.
In yet another embodiment, the auxiliary information are text data relating to the first program. Under the embodiment, the VCR has means responsive to user input for storing the text data in a memory so that they can be displayed at selected time.
In another embodiment, a library containing the directories of a plurality of selected tapes is stored in the VCR. The availability of the library facilitate searching of programs among the plurality of tapes.
In still another embodiment, broadcast programs are classified into different categories. The identification of the category of a broadcast program is broadcasted in its VBI. According to the embodiment, the category identification is retrieved from the VBI and stored as part of the directory information, which can later be used to facilitate searching of a specific category of programs from an archive of tapes.
In a preferred embodiment, a hybrid VCR system is capable of detecting the address and the tape identification number (TID) from either the control track or the VBI of a video tape and identifying the type of tape therefrom. A first type of tape is a home recorded tape (HR tape) in which the directory thereof is stored in a RAM and the TID and the address are stored in the control track in a first embodiment and in the VBI in a second embodiment. A second type of tape is a prerecorded tape (PR tape) from a publisher in which the directory is stored in the VBI and the addresses are stored in a similar manner to the HR tapes. A third type of tape is a retroactively indexed tape (RI tape) which was previously recorded without an index and to which an index is being added. A directory is created in the RAM and the TID and addresses are recorded in the control track.
The address is determined from the location of the recording on the tape as a distance from the beginning of the tape. In a first embodiment, the address is determined by counting the spindle rotation either by counting the number of pulses reflected from light reflective lines on the spindle or calculating the length from the number of sync pulses recorded on the tape. In a second embodiment, the distance is determined by measuring the rotation of a capstan that rotates in unison with the tape movement.
In a first embodiment, the address system is a file mark plus a synchronous sprinkling address system (FMAS). This system writes the absolute address on the control track in the form of address packets. These packets are written in two types of locations. The first type (type 1) is written at the beginning of each program and at the end of the last program on the tape. The main function of these packets is to serve as xe2x80x9cfile marksxe2x80x9d for search of starting points of programs. The second type of packet (type 2) is asynchronously recorded as often as possible in between the type 1 packets. These packets serve as xe2x80x9croad marksxe2x80x9d for determining current tape location.
In a second embodiment, two separate address systems are used. A high resolution address system (HRAS) writes an absolute address at high repetition rate (e.g., once every few seconds) on a line of the VBI. The second type of address system is a low resolution address system (LRAS) where the absolute address is written on the control track at the beginning of each program as well as the end of the last program as an address mark. An alternate LRAS is to write only marks, such as VISS or VASS marks in the control track at the beginning of each program on the tape and at the end of the tape.
The TID is generated by seeding a random number generator with the time of the first usage of the VCR so that the probability of two VCRs having the same identification number is reduced. The TID also includes a tape number.
Multiple indexing VCRs may be interconnected on a bus for transferring directory data therebetween. In a specific implementation, a household may have several VCR systems that will play some video tapes in both systems. The interconnection allows the directory to be transferred between multiple VCRs so that each VCR has the same directory library.
In yet another embodiment, an input/output port is provided so that the user may connect the VCR system to a printer or another external device such as a telephone line or a floppy disk drive. The directory or auxiliary information broadcast with a program may be printed in hard copy.